ABSTRACT
The Forties Oilfield (the largest in the U.K. sector of the North Sea) has been in production since September 1975. In June 1975, a quantitative survey of the benthic sediments and fauna over the area was made at the start of an environmental monitoring program for the field. The results of a repeat survey carried out after three years of production have been reported by Hartley.13 This paper presents data from a third similar survey in June 1981 and compares the findings with those of the earlier surveys.
The benthic fauna of the Forties Field is rich and diverse and qualitatively corresponded well in 1981 to previous descriptions. Naturally occurring gradients in both the sediment type and fauna are a feature of this area. Changes in the densities of certain species were noted at some sites in 1981, including increases in certain opportunistic forms. Although no areas of biological effect could be delineated around the four production platforms, the industrial activity in the field may be implicated in the changes found at several stations. The hydrocarbon content of the sediments was low and, with one possible exception, did not appear related to the biological changes noted.
The results to date suggest that offshore oilfields in deep water, developed using water-based drill fluids, present relatively few biological problems in the short term. Since no major biological effects have been found after six years of drilling and production, a reduced program of monitoring is recommended to maintain biological surveillance during the life of the field.
Tributyltin inputs to the North Sea from shipping activities, and potential risk of biological effects